Wang, Z., Chen, C., Wang, J., Suess, E., Chen, X., Ma, X., Wang, G., Xiao, S., 2020. Wide but not ubiquitous distribution of glendonite in the Doushantuo Formation, South China: Implications for Ediacaran climate. Precambrian Research 338, 105586.

http://www.sciencedirect.com/science/article/pii/S030192681930470X Glendonites are pseudomorphs of syndepositional or early authigenic ikaite (CaCO ·6H O) that often forms at 3 2 near-freezing temperatures. Silicified glendonite has been reported from inner-shelf deposits of the lower Ediacaran Doushantuo Formation at a single stratigraphic section in South China, where they are 13 13 stratigraphically associated w ith the positive δ C excursion EP1 but predate the negative δ C excursion EN3 (=Shuram excursion), indicating a period of cool climate somewhere between ~609 Ma and ~551 Ma. This interpretation predicts a wider geographic distribution of Ediacaran glendonites in equivalent strata in the Yangtze Block of South China. To test this prediction, we conducted a regional survey of Doushantuo Formation and found that, although glendonites are not universally present, they occur in expected stratigraphic intervals and in association with EP1 at two new sections representing inner-shelf and intrashelf basin facies. The wide but not ubiquitous distribution of Doushantuo glendonites indicates that ikaite precipitation and glendonite formation was controlled by both regional climatic and local geochemical factors. Glendonites at the new localities are stellate clusters pseudomorphed by calcite spar and sometimes are rimmed with silica. The 13 calcite spar is characterized by highly variable and mostly negative δ C values as low as -37‰, indicating that diagenetic transformation of precursor ikaite to calcitic glendonite may be related to anaerobic oxidation of organic matter or methane in sediment. The new data suggest an early Ediacaran cold period prior to EN3 or the Shuram excursion and facilitation of glendonite/ikaite formation by both climatic and local geochemical conditions such as redox conditions and phosphate concentrations.

Wang, Z., Nelson, D.D., Dettman, D.L., McManus, J.B., Quade, J., Huntington, K.W., Schauer, A.J., Sakai, S., 2019. Rapid and precise analysis of carbon dioxide clumped isotopic composition by tunable infrared laser differential spectroscopy. Analytical Chemistry 92, 2034-2042.

https://doi.org/10.1021/acs.analchem.9b04466 The high precision measurement of doubly substituted ('clumped') isotopologues in CO is a topic of 2 significant interest in isotope geochemistry. Here we describe the performance of a new isotope ratio laser spectrometer using tunable infrared laser differential absorption spectroscopy (TILDAS). The TILDAS instrument has two continuous-wave lasers to simultaneously measure the four isotopologues involved in the 12 16 13 16 18 13 16 12 16 18 ⇆ C O + C O O C O + C O Oexchange reaction. CO samples are trapped in a low volume 2 2 2 ∼ ( 250 mL) optical multipass cell with a path length of 36 m. Each sample is compared to a reference gas, and clumped isotopologue precision of 0.01‰ (SE) is achieved within 20 min for 15 μmol samples. Similar precision is also achieved for bulk isotopic composition. The degree of rare isotope clumping in excess of strictly random distribution (Δ ) measured by this TILDAS instrument varies linearly with theoretically 16O13C18O calculated values and shows a very weak dependence on bulk isotopic composition.

Weber, A.L., Rios, A.C., 2019. Imidazolium-catalyzed synthesis of an imidazolium catalyst. Origins of Life and Evolution of Biospheres 49, 199-211.

https://doi.org/10.1007/s11084-019-09589-2 The chemistry of imidazolium-catalyzed imidazolium synthesis was studied as part of an effort to develop a plausible prebiotic synthesis of a small catalytic molecule capable of catalyzing its own synthesis. Specifically, we investigated the one-pot 1-ethyl-3-methylimidazolium acetate (EMIM-Ac) catalyzed synthesis of 1,3- dibutyl-4,5-difuryl-imidazolium acetate (DBDFIM-Ac) from furfural, n-butylamine, formaldehyde, and acetic acid at 80 °C. Liu et al. (2012) had previously demonstrated the first reaction of the synthetic process, the EMIM-Ac catalyzed benzoin condensation of furfural that yields furoin. Our early studies established the n- second reaction of the synthetic process, the multicomponent reaction of furoin, butylamine, formaldehyde,